1. Field of the Invention
The present invention generally relates to cooling structures for integrated circuit element modules, and more particularly to a cooling structure for removing heat generated in integrated circuit element modules.
Recently, the density of mounting integrated circuit elements has been increased, and the amount of heat generated in integrated circuit elements themselves has increased. It has become more difficult to cope with heat by a conventional forced cooling system. Nowadays, it is required to provide an improved cooling system having a higher capability of cooling integrated circuit elements.
2. Description of the Prior Art
FIG. 1 is a partially sectional, perspective view of a device having a conventional cooling structure for integrated circuit elements, as disclosed in Japanese Laid-Open Patent Application No. 59-202657. Further, FIG. 2 is a cross-sectional view taken along a line A--A shown in FIG. 1. As shown in FIGS. 1 and 2, a plurality of integrated circuit elements 3 are mounted on a circuit board 1. Heat sinks 4 are respectively attached to the integrated circuit elements 3. Each of the heat sinks 4 may have a number of fins. In the example being considered, the integrated circuit elements 3 with the heat sinks 4 are referred to as integrated circuit element modules 2. A duct 5 is provided above the circuit board 1. A plurality of holes 6 are formed in a bottom part 5a of the duct 5 so that the holes 6 face the heat sinks 4. Blowers or fans 7 are provided to supply air to the duct 5.
The cooling structure shown in FIG. 1 operates as follows. Heat generated in the integrated circuit elements 3 is conducted to the heat sinks 4. Air is supplied to the duct 5 by the blowers 7, and arrives at the heat sink 4, which are cooled by the air. Hence, the integrated circuit elements 3 connected to the heat sink 4 are cooled.
The thermal resistance .THETA.fa (.degree.C./W) between a fin of a heat sink and a coolant (air in the example being considered) is a parameter representing the cooling performance of the fin. The thermal resistance can be written as follows: EQU .THETA.fa=1/(Af.multidot.h)
where Af denotes the effective area (m.sup.2) of the fin, and h denotes the average thermal conductivity (W/m.sup.2 K) .
In the cooling structure for the integrated circuit element modules shown in FIGS. 1 and 2, there are spaces (opens) between the bottom surface 5a of the duct 5 and the heat sinks 4. If the fins are miniaturized to increase the effective area Af to thereby improve the cooling performance, a large loss of pressure is caused by the fins. The above large loss leads to preventing air from passing through the fins and thus reducing the average thermal conductivity h. As a result, the cooling performance (the thermal resistance .THETA.fa) is restricted to a certain level.
Air supplied to the integrated circuit element modules 2 located on the downstream side of flow, in other words, away from the blowers 7 has an increased temperature due to heat generated in the modules 2 located on the upstream side thereof. Hence, these modules 2 cannot be cooled effectively and efficiently.